GlusterFS is a clustered file-system capable of scaling to several
peta-bytes. It aggregates various storage bricks over Infiniband RDMA
or TCP/IP interconnect into one large parallel network file
system. GlusterFS is one of the most sophisticated file system in
terms of features and extensibility.  It borrows a powerful concept
called Translators from GNU Hurd kernel. Much of the code in GlusterFS
is in userspace and easily manageable.
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WWW: http://www.gluster.org/